ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus PublicationsGöttingen, Germany10.5194/acp-11-5277-2011Homogenous nucleation of sulfuric acid and water at close to atmospherically relevant conditionsBrusD.12NeitolaK.2HyvärinenA.-P.2PetäjäT.3VanhanenJ.3SipiläM.3PaasonenP.3KulmalaM.3LihavainenH.21Laboratory of Aerosol Chemistry and Physics, Institute of Chemical Process Fundamentals Academy of Sciences of the Czech Republic, Rozvojová 135, 165 02 Prague 6, Czech Republic2Finnish Meteorological Institute, Erik Palménin aukio 1, P.O. Box 503, 00100 Helsinki, Finland3Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland06062011111152775287This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from http://www.atmos-chem-phys.net/11/5277/2011/acp-11-5277-2011.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/5277/2011/acp-11-5277-2011.pdf

In this study the homogeneous nucleation rates in the system of sulfuric
acid and water were measured by using a flow tube technique. The goal was to
directly compare particle formation rates obtained from atmospheric
measurements with nucleation rates of freshly nucleated particles measured
with particle size magnifier (PSM) which has detection efficiency of unity
for particles having mobility diameter of 1.5 nm. The gas phase sulfuric
acid concentration in this study was measured with the chemical ionization
mass spectrometer (CIMS), commonly used in field measurements. The wall
losses of sulfuric acid were estimated from measured concentration profiles
along the flow tube. The initial concentrations of sulfuric acid estimated
from loss measurements ranged from 10<sup>8</sup> to 3 × 10<sup>9</sup> molecules cm<sup>−3</sup>. The nucleation rates obtained in this study cover about three
orders of magnitude from 10<sup>&minus;1</sup> to 10<sup>2</sup> cm<sup>&minus;3</sup> s<sup>&minus;1</sup> for
commercial ultrafine condensation particle counter (UCPC) TSI model 3025A
and from 10<sup>1</sup> to 10<sup>4</sup> cm<sup>&minus;3</sup> s<sup>&minus;1</sup> for PSM. The nucleation
rates and the slopes (<i>d</i>lnJ/<i>d</i>ln [H<sub>2</sub>SO<sub>4</sub>]) show satisfactory agreement
when compared to empirical kinetic and activation models and the latest
atmospheric nucleation data. To the best of our knowledge, this is the first
experimental work providing temperature dependent nucleation rate
measurements using a high efficiency particle counter with a cut-off-size of
1.5 nm together with direct measurements of gas phase sulfuric acid
concentration.